Averaged Spinal Evoked Potentials to peroneal nerve stimulation which arise in the dorsal roots of the cauda equina and in spinal cord afferent pathways will be recorded from surface electrodes attached to the skin over the spine of human patients of all ages with diffuse of focal disease of the spinal cord and compared with similar potentials recorded in normal subjects. Scalp recorded potentials to peroneal nerve stimulation will also be recorded in these patients. The clinical usefulness of these methods in the evaluation of these patients will be investigated. Somatosensory evoked short latency potentials to median nerve stimulation which arise in subcortical and cortical structures will be recorded from the scalp of patients of all ages with focal and diffuse neurological disease and compared with similar potentials obtained in normal subjects to determine whether this method is clinically useful in localizing lesions in the nervous system and in the evaluation of these patients. The effect of maturation on these potentials will also be studied.